Need help id this white stuff on rock lol

[Jriv86]

Hi so this tank is about 1.5 months old. I lifted the live rock to clean substrate and these white string things were over the bottom. Are they harmful? Should I leave them. Thank you in advance for your help.

 

[ReefRusty]

Any photos?

 

[supernanoguy]

Most likely sponges. Cant say much without photos.

 

[Jriv86]

Sorry didn't know my previous pics didn't upload because they were to big.

 

[supernanoguy]

Yea hard to tell. Sorry can’t help.

 

[ReefRusty]

Does it move or stuck to the rock? It looks like poriferan sponge and harmless. Believe you can leave it or trim it. Someone can correct me if im wrong here. Also still learning everyday

 

[Jriv86]

Does it move or stuck to the rock? It looks like poriferan sponge and harmless. Believe you can leave it or trim it. Someone can correct me if im wrong here. Also still learning everyday

I lifted the rock and gave it a good shake underwater and it didn't come off.